More #LK99 good/bad news. Good news is more results have been reported. Bad news is exactly the same. NTU, an excellent university which has sent its students as PhD students and postdocs to CMTC over the years, reports insulating resistivity increasing with decreasing T and...
some diamagnetism (they are continuing their LK99 experiments) and NPL, a top govt lab in India, reports no SC and some diamagnetism in its latest arXiv posting. It is now increasingly difficult to give the benefit of the doubt to the OP by Lee et al
An important preprint tonight is from ICQM, a top research center in China (which has several CMTC alumni in its faculty), finds no SC, but small amount of ferromagnetism (not diamagnetism) in tiny flakes of LK99 samples. No SC at all in all 3 reports arxiv.org/abs/2308.03110
One aspect of ICQM and NTU (also NPL) results is the extreme high semiconducting/insulating resistivity (increases with decreasing T) with the room temperature resistivity ~ 2.10^5 which is billion times the Cu resistivity. LK99 seems to be an Anti-SC! https://t.co/1Fj69whOITohm.cm
Enquiring minds want to know: Is diamagnetism not interesting? The answer is that NO, diamagnetism is NOT interesting, many materials (e.g. Pb, Cu, P going into LK99) are diamagnetic. It is a run of the mill property. (There are more results, but CMTC cannot divulge them yet.)
With a great deal of sadness, we now believe that the game is over. LK99 is NOT a superconductor, not even at room temperatures (or at very low temperatures). It is a very highly resistive poor quality material. Period. No point in fighting with the truth. Data have spoken.
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Since CMTC produced many papers on flatbands and on superconductivity (rarely together), we are delighted seeing flatbands of LK99 being discussed everywhere, this can only be good. In case, you are still confused, flatbands in the simplest terms imply 'very heavy electron mass'
Why is heavy mass important? Because large mass means slow motion, and slow motion means low kinetic energy, and this means that the effects of interactions among electrons become very important, making the system 'strongly correlated', something we theorists love because the...
problem becomes extremely complicated as we must solve 10^23 electrons strongly interacting together, and theoretical physicists love difficult problems-- band structure calculations producing flatbands immediately become suspect since band theory neglects interactions
CMTC has received SO MANY requests to provide an update on LK99 that we are breaking our 'sign-off' since our tweets are only for the purpose of precise scientific outreach from our critical perspective, So, here we go...
Several groups have made LK99, most impressively in a 'garage' in LA under live streaming, here is the first arXiv-posted 'synthesis', but these reproductions mean little since an alloy of Pb/Cu/P/O is fragile and may have different forms/properties arxiv.org/abs/2307.16402
Only relevant questions are: does it superconduct and does it do so at 300K? These questions have not been addressed by anybody yet, and the euphoria about making LK99 in other labs is misplaced until SC is reported. Independent synthesis of LK99 is a minor, but necessary, step
What is a superconductor?The answer that it is a material with zero electrical resistance, current flows even after the battery is disconnected in a closed circuit, is necessary, but insufficient. A perfect metal with no impurities has zero resistance, but it is no SC!
The most necessary empirical condition for SC is that it expels magnetic flux, if you apply a magnetic field to a SC, it expels the field lines. This is called the Meissner effect. Zero resistivity is a derivative property, which is of course, spectacular, but less fundamental
Another characteristic feature of a SC is that the electrical resistance drops to zero 'suddenly' at some temperature T_c, the critical temperature. In non-SC metals, the resistance R keeps on decreasing with temperature T as a power law: R~ T^a where a ~1-2 typically
Conceptually there is nothing special or impossible about room temperature or much higher temperature superconductors except they have not been decisively observed. After all ferromagnets exist with high Curie temperatures ~ 1400 F (Fe), 2100 F (Co), and we take them as given!
Both ferromagnet and superconductor are characterized by energy gaps in the quantum spectra, and it just so happens that this energy gap is huge (tiny) in ferromagnets (superconductors), and the critical temperature depends directly on this energy gap. What determines this gap?
Something called 'coupling constant' which defines the effective 'strength' of the microscopic quantum interaction leading to the specific phenomenon, and it just so happens that the coupling constant for magnetism (superconductivity) is large (small).
It is now time to do the unpleasant: deconstruct the non-experimental parts of the Korean room temp SC claims. This is relevant because the theoretical/background SC discussions in these papers are so naïve that if it were an undergraduate project at Maryland we would give an F
First, strange sentences throughout both papers showing that the authors know little to nothing about SC. We emphasize that their ignorance about SC theories does not necessarily invalidate their experimental findings, but it raises serious issues about their expertise...
"To discover a room-temperature superconductor, observing the emergence of a metallic phase through an insulator-to-metal transition (IMT) at temperatures higher than room temperature is crucial"
We have no idea what this means-- 3D SC is not a metal-insulator transition ever
Quantum computing/information started as a subject in 1994 with the simultaneous theoretical breakthroughs of efficient integer factorization and quantum error correction, eventually leading to the concept of fault tolerant (FT) QC both as disrutive science and technology ..
Often it is claimed that QC began in the 1980s and indeed a few people including Feynman talked about QC, but the community paid no attention whatsoever since QC was just science fiction without fault tolerance, and the consensus was that quantum decoherence cannot be corrected
The actual science, not the fantasy, began in 1994 with the concept of quantum error corrected FTQC based on logical qubits carrying out integer factorization as a disruptive goal becoming real